Treatment of nickel-copper-aluminum alloys



Patented June 26, 1928.

TRUMAN S. FULLER, F SGHENECTADY,

TREA'IMENT OF NICKEL-COPPER-ALUH INUM ALLOYS.

'No Drawing.

, The present invention relates to alloys of nickel, copper and aluminum/in which the two former metals predominate.

Alloys consisting of about 60 to 75 parts of nickel and about 25 to 40 parts copper have been used in the industrial artsbecause of their resistance to corrosion, and good physical properties. For some purposes however the moderately low elastic limit of this'type of alloy has been aserious handicap, particularly when these alloys have been used for the construction of devices subjected to severe mechanical strains and shocks, as for example for turbine buckets or similar rapidly rotating parts.

In accordance with the invention ofi Eric T. Asp an improved forgeable alloy of nickel, copper and aluminum has been produced which also is highly resistant to corrosion.

4 As described and claimed by him in a copending applicatioii, SeriaLNo. 699,895, filed March 17, 1924, this forgeable alloy ismade by'mixing aboutone-tenth of one per cent of magnesium with the molten ternary alloy prior to casting. The aluminum content preferably should. be maintained between about 2.0 to 3.5 per cent to get best results although variations between about one-half per cent to five per. cent are permissible. All of the proportions given herein are by weight. I have discovered "that the alloy produced by Asp can be greatly improved b a deforming treatment below 1000? C. whic together with the product constitutes my inventioIT.

In accordance with my present invention, I have provided an improved, alloy of nickel, copper and aluminum which has physical properties superior to the alloy produced by Asp, such as a higher tensile strength,"high elastic limit and higher ductility. The alloy, when worked under the most favorable conditions, has a physical strength com parable to the alloy steels, while retaining the desirable corrosion-resisting properties of the nickel-copper alloys. The carbon content drdinarily should be within the limits of, .03 to 0.4 per cent. In general for the best results,,when the aluminum content is high, the carbon content.

should be low, and conversely with an aluminum content of the lower values of the range above. given, the carbon content may be higher. Excellent results have been ob- Applicatlon filed March 17, 1924. Serial No. 699,894.

tained with alloys having an aluminum content of about 3 to 3.5 per cent with a carbon content in the neighborhood of about .08 per cent; while equally good results have been obtained with alloys having an aluminum content of about 2 per cent and a carbon content of 0.14 to 0.16 per cent.

In -order to produce the most desirable physical properties in the alloy the final def- .ormation orworking'of the alloy must be carried on at a temperature below 900 C.

In carrying my invention into'eftect, an alloy of copper and nickel is prepared by the well known methods of the'art. The'nickel content'may be va'iied considerably, but ordinarily should be as high as 50 per cent, the

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copper content being lv'aried correspondingly,

that is the copper content being increased .as the nickel content is decreased. The nickel and copper may be alloyed with'one another. by simple fusion and the required amount of aluminum may be simply. stirred into the moltenv nickel-copper alloy. Preferably about 1.5 parts by weight of manganese and about 2.5 parts by weight of iron are added to the melt prior to the addition of alumi num. As already indicated the carbon content desired depends, upon the amount of aluminum present. In accordance with the invention of the above Asp application,

about one-tenth of one per cent of magnesia um by weightis stirred into the melt, and

the alloy then is cast into an ingot mold.

The cast ingots are workable, that is, capa-v Ible of being wrought, asby forging or rolling. When the'metal is forged. at a temperature in the neighborhood of 1000 C.v the physical propertles of the product are ingen- 'eral similar to the physical properties of the corresponding nickel-copper all-0y. When,

however, in accordance with-my invention, after some deformation has occurred," the deformation is continued at a lower temperature, the physical properties are improved. to a radical degree, the improvement be-- coming more 'narked with the lowering of the final deformation temperature down to roomtemperature. However, below 600 C.

but-little additional change is produced in tensile strength.-

' For example, when'ingots'of an alloy of about parts nickel, 35 parts copper and containing (byanalysiszg" about'3. 0 to 3.5-

parts of aluminum and a out 0.1 per cent of "carbon, which have been forged at about 1000- C.'to reduce the diameter to about one-half the original value, are forged sub- 110,000 pounds per sq. inch with a ,retention of high ductility. When finishing at ap proximately room temperature a tensile strength of 17 5,000 pounds, and the remarkably high elastic limit of 131,000 pounds with high ductility are produced.

These excellent physical properties cou-v pled with non-corrodibility render the alloy valuable for the manufacture of turbine buckets, springs and marine parts, such as propellers and condenser tubes.

' What I claim as new and desire to secure by Letters-Patent of the United States, is

l. The process of improving the physical properties of an alloy consisting-largely of nickel and copper and a relatively small amount of aluminum which consists in deforming said alloy at a temperature of about 1000 C. and thereafter finishing the deformation at a temperature materially lower than 1000 C. but above 500 C.

2. The process of improving the physical properties of an alloy consisting largely of nickel and copper and containing a few per cent of aluminum whichconsi-sts in initially deforming said alloy at a temperature below- 1000 C. and continuing the deformation at temperatures approaching 600 .C. v

3. The process of improving the mechanical strength while retaining the ductility of an alloy consisting of at least about parts nickel, about 25 to 40 parts copper about one-half to five parts aluminum, and a small amount of carbon having been rendered forgeable by treatment with magnesium, which consists in maintaining thecarbon content of said alloy within the range of about 0.03 to 0.40 parts with respect to the aluminum content so that a higher aluminum content'will be accompanied b a lower carbon content, deforming said alloy at a temperature of. about 1000 C. and there after again deforming the alloy at a temperature materially below 1000 C. but above 500 C. 4. The process of improving the physical properties of an alloy comprising about parts nickel, about 35 parts copper, about three parts of aluminum and a fractional part of carbon which consists in forging said alloy at temperatures within the range of l000 to 600 C. the forging being begun in the upper part of said range and completed in the lower part of said range.

5. The process of improvingthe physical.

properties of an alloy consisting largely of copper and nickel, the nickel being in excess of the copper, and containing one half to five parts aluminum, which consistsin. de-

. forming the alloy at a temperature of about 1,000 C. and'again deforming the alloy at a temperature materially lower than 1000. C. but above 500 C.

In witness whereof, I have hereunto set my hand this 15th day of March, 1924.

TRUMAN S. FULLER. 

